This invention relates to a flatly folded bag where only the mouth, for receiving articles, is in an unsealed state while other parts are completely sealed. In the inventive article packing bag, the mouth is opened by blowing air toward the mouth and thus the articles can be thrown into the bag through the mouth, while the mouth is kept open.
The mouth of the packing bag must be opened by mechanical means for automatically packing the articles into the bags. It is well known to use suction discs in a technique for opening such bags. The use of suction discs, however, involves a problem, since the structure becomes complicated e.g. in the mechanism for actuating the discs or in the vacuum mechanism.
Therefore, as means of opening the mouth of bags without using these suction discs, Japanese utility model application No. 57-159323 teaches the usefulness of sending air toward the mouth of the bags and utilizing the force of this air to open the bags. FIG. 7 illustrates the bag of this patent application. This bag 01 has a back face 03 which is top most as illustrated in FIG. 7. Back face 03 includes slits 05 and 05' each having a certain length from the brim 02 of the bag mouth. The slits are at metrical positions with respect to a central joint section 04 in the back face 03. Joint section 04 is also positioned between hooking holes 06 and 06', provided at positions oppositely facing slits 05 and 05', on a front face 70 of the bag. When air is blown in the direction of the arrow marked "a", the air is accepted into the bag 01 to allow the slits 05 and 05' to rise on and escape from a lock metal 08 which extends through the slits and through holes 06 and 06'. The air also opens the mouth of bag 01. Articles are then thrown into the bag 01 while the mouth is kept opened. When the charging of articles is completed, the bag 01 is pulled in the direction of the arrow marked "b". When the bag 01 is pulled, the hooking holes 06 and 06' are to be torn from the lock metal 08.
This type of bag, however, requires much trouble in its preparation because the gap between legs of the lock metal 08 must always coincide with the gap between the slits 05 and 05' since the slits must slide past the lock metal 08 in two straight lines on the right and left. The legs of the lock metal 08 must meet the gap of slits 05 and 05' and this may not happen if there is a difference in the dimensions of bag 01. Further, because of the shape of slits 05 and 05', the lock metal 08 oftens touches edges of slits 05 and 05' and the degree of opening for the mouth for successive bags 01, differ from one bag to the next. This causes trouble in charging articles into the bags since the edges of slits 05 and 05' may be hooked by the lock metal 08.
Also, since the hooking holes 06 and 06' are open against the slits 05 and 05', and are circular it is difficult to tear the bag from lock metal 08 when it is pulled in the "b" direction and further the direction of tearing is not stable. The mouth portion of bag 01 is thus often disturbed, resulting in a bad appearance for the bag.